SQL - Basics

Question 1

SELECT

Answer 1

extracts data from a database

Question 2

UPDATE

Answer 2

updates data in a database

Question 3

DELETE

Answer 3

deletes data from a database

Question 4

INSERT INTO

Answer 4

Inserts new data into a database

Question 5

CREATE DATABASE

Answer 5

creates a new database

Question 6

ALTER DATABASE

Answer 6

modifies a database

Question 7

CREATE TABLE

Answer 7

creates a new table

Question 8

ALTER TABLE

Answer 8

modifies a table

Question 9

DROP TABLE

Answer 9

deletes a table

Question 10

CREATE INDEX

Answer 10

creates an index (search key)

Question 11

DROP INDEX

Answer 11

deletes an index

Question 12

SELECT * FROM Customers;

Answer 12

Selects all the records in “Customers”
* = select all

Question 13

SELECT DISTINCT Country FROM Customers;

Answer 13

Selects only different “countries” from customers.
Note: Without the “DISTINCT” it would have duplicates.
The distinct removes duplicates and only shows a list of different ones.

Question 14

SELECT Count(*) AS DistinctNumber
FROM (SELECT DISTINCT Country FROM Customers);

Answer 14

Selects the number of different countries. The “AS” Sets a name for the column. As there is two select features, you need the other one in brackets. “FROM” needs to be before the start of the bracket so we know where we are getting the info from.

Note: If there’s multiple Commands, the others need to be in brackets.

Question 15

SELECT * FROM Customers
WHERE country = ‘Mexico’;